Page 1 of 2 12 LastLast
Results 1 to 10 of 15

Thread: telnet connection delay

Hybrid View

  1. #1

    Default telnet connection delay

    Hello!


    When trying to connect with something after


    admin@linux-tlpp:~> telnet 192.168.1.1

    <--- here for some reason there is a delay

    Trying 192.168.1.1...
    Connected to 192.168.1.1.
    username:



    admin@linux-tlpp:~> cat /proc/version
    Linux version 4.12.14-lp151.28.7-default gcc version 7.4.0 (SUSE Linux)

    admin@linux-tlpp:~> time telnet 127.0.0.1
    Trying 127.0.0.1...
    telnet: connect to address 127.0.0.1: Connection refused
    real 0m5,068s
    user 0m0,002s
    sys 0m0,000s

    admin@linux-tlpp:~> cat /etc/nsswitch.conf
    passwd: compat
    group: compat
    shadow: compat
    hosts: dns files
    networks: files dns
    services: files
    protocols: files
    rpc: files
    ethers: files
    netmasks: files
    netgroup: files nis
    publickey: files
    bootparams: files
    automount: files nis
    aliases: files


    admin@linux-tlpp:~> cat /etc/resolv.conf
    nameserver 10.10.0.111
    nameserver 10.10.2.20
    nameserver 8.8.8.8

  2. #2
    Join Date
    Jun 2008
    Location
    Auckland, NZ
    Posts
    20,769
    Blog Entries
    1

    Default Re: telnet connection delay

    I can only speculate here, but any delay with authenticating will be down to the server you're connecting to, so that's probably where you should focus your attention. This could be a security mechanism to limit brute force attack attempts for example.
    openSUSE Leap 15.1; KDE Plasma 5

  3. #3

    Default Re: telnet connection delay

    Quote Originally Posted by deano_ferrari View Post
    I can only speculate here, but any delay with authenticating will be down to the server you're connecting to, so that's probably where you should focus your attention. This could be a security mechanism to limit brute force attack attempts for example.

    The problem is on my PC. From other hosts, everything is fine. I am inclined to think that the matter is in reverse resolv.

  4. #4
    Join Date
    Jun 2008
    Location
    Netherlands
    Posts
    25,583

    Default Re: telnet connection delay

    Quote Originally Posted by gorn View Post
    I am inclined to think that the matter is in reverse resolv.
    And what if you do a reversed reolve yourself?
    Code:
    nslookup 192.168.1.1
    or
    Code:
    host 192.168.1.1
    Henk van Velden

  5. #5

    Default Re: telnet connection delay

    Quote Originally Posted by hcvv View Post
    And what if you do a reversed reolve yourself?
    Code:
    nslookup 192.168.1.1
    or
    Code:
    host 192.168.1.1

    admin@linux-tlpp:~> host 192.168.1.1

    Host 1.1.168.192.in-addr.arpa. not found: 3(NXDOMAIN)

  6. #6
    Join Date
    Jun 2008
    Location
    Netherlands
    Posts
    25,583

    Default Re: telnet connection delay

    Quote Originally Posted by gorn View Post

    admin@linux-tlpp:~> host 192.168.1.1

    Host 1.1.168.192.in-addr.arpa. not found: 3(NXDOMAIN)
    (Please CODE tags)
    I can understand the result, but I can not see if there was a delay. And that is where the test should be done for.
    Henk van Velden

  7. #7
    Join Date
    Jun 2008
    Location
    San Diego, Ca, USA
    Posts
    11,695
    Blog Entries
    2

    Default Re: telnet connection delay

    Aside from your problem,

    I caution you to never run a telnet server.
    Telnet sessions send your credentials and session content in clear text.
    Use ssh instead.

    I use the telnet client only in my troubleshooting toolbox to probe ports on remote machines, nothing more.

    TSU
    Beginner Wiki Quickstart - https://en.opensuse.org/User:Tsu2/Quickstart_Wiki
    Solved a problem recently? Create a wiki page for future personal reference!
    Learn something new?
    Attended a computing event?
    Post and Share!

  8. #8
    Join Date
    Jun 2008
    Location
    San Diego, Ca, USA
    Posts
    11,695
    Blog Entries
    2

    Default Re: telnet connection delay

    Quote Originally Posted by gorn View Post

    admin@linux-tlpp:~> host 192.168.1.1

    Host 1.1.168.192.in-addr.arpa. not found: 3(NXDOMAIN)
    That means your machine sent a hostname query to your DNS,
    And your DNS doesn't have a reverse lookup zone configured.

    That's curious that your machine might read an IP address as a hostname and not as an IP address...
    Are you sure your machine is set up for same network (and netmask) so that if the remote address isn't on your network that your machine knows to use your DG?
    eg
    If your machine has an address 192.168.2.1/16
    and the machine with address 192.168.1.1 is on another physical network.

    TSU
    Beginner Wiki Quickstart - https://en.opensuse.org/User:Tsu2/Quickstart_Wiki
    Solved a problem recently? Create a wiki page for future personal reference!
    Learn something new?
    Attended a computing event?
    Post and Share!

  9. #9
    Join Date
    Jun 2008
    Location
    Netherlands
    Posts
    25,583

    Default Re: telnet connection delay

    Please Tony, read above why we use this DNS lookup. It is only to find out of a (any) reversed lookup gives an uwanted delay as encoutered in the OPs telnet session. If there is a answer or a "not found" is of no importance here.
    Henk van Velden

  10. #10
    Join Date
    Jun 2008
    Location
    San Diego, Ca, USA
    Posts
    11,695
    Blog Entries
    2

    Default Re: telnet connection delay

    Quote Originally Posted by hcvv View Post
    Please Tony, read above why we use this DNS lookup. It is only to find out of a (any) reversed lookup gives an uwanted delay as encoutered in the OPs telnet session. If there is a answer or a "not found" is of no importance here.
    Ok,
    Then consider my post 2 separate responses...

    The warning about running telnet server is based entirely on the very first post.
    The part about doing a reverse lookup, I'm not clear what you were trying to investigate, machines fundamentally communicate by MAC address and on top of that the IP address... Machines don't actually communicate by name so names have to be resolved to IP addresses... but the reverse isn't typically true. Bottom line, a reverse lookup wouldn't happen for an attempted telnet connection, reverse lookups are useful only for more complex analytical applications, not simple network connections.

    Typically, latencies for simple connections like telnet are network related, typically not system.
    So, recommend using the most obvious tool for initially testing latency... PING and if you're traversing multiple routers, traceroute.

    TSU
    Beginner Wiki Quickstart - https://en.opensuse.org/User:Tsu2/Quickstart_Wiki
    Solved a problem recently? Create a wiki page for future personal reference!
    Learn something new?
    Attended a computing event?
    Post and Share!

Page 1 of 2 12 LastLast

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •